A hydrothermal reconstruction-precise lithium supplement process

Abstract

The application discloses a kind of hydrothermal reconstruction-precise lithium supplement process, belong to waste battery recycling and reusing technical field;Hydrothermal reconstruction-precise lithium supplement process, comprising the following steps: (1) the positive plate in waste lithium ion battery is sintered, sieved, and D-NCM111 is obtained;(2) water is added to D-NCM111 and hydrothermal reaction is carried out, then water washing, drying are sequentially carried out, and hydrothermal product (H-NCM111) is obtained;(3) hydrothermal product (H-NCM111) and lithium source are added to solvent, and grinding is carried out, and lithium supplement product (H-NCM111-Li) is obtained;(4) lithium supplement product (H-NCM111-Li) is annealed, and renewable material (R-NCM111) is obtained.The layered structure of the material is repaired by the hydrothermal method, the consumption of lithium source is reduced, the crystal structure and electrochemical performance of NCM111 material are restored, and the first circle discharge specific capacity reaches 138mAh g ‑1 1C rate under 100 times 1C rate charge-discharge cycle stability is basically equivalent to commercial C-NCM111 material, indicating that its cycle stability is good.The process is simple, energy consumption and pollution emission are reduced, and has industrial application potential.

Description

Technical Field

[0001] This invention belongs to the field of waste battery recycling technology, and particularly relates to a hydrothermal reconstruction-precision lithium replenishment process. Background Technology

[0002] Battery recycling technologies mainly include pyrometallurgy, hydrometallurgy, biometallurgy, and direct regeneration technologies, each with its own characteristics in terms of resource reuse and environmental protection.

[0003] Pyrometallurgy is a traditional recycling process with advantages such as large processing capacity, strong adaptability to raw materials, and high recovery rate of valuable metals. It also allows for the reuse of some materials. However, pyrometallurgy also has significant drawbacks, including high energy consumption, the generation of pollutants such as waste gas and slag, substantial equipment investment, and the inability to achieve selective recycling, potentially leading to resource waste.

[0004] Hydrometallurgy extracts valuable metallic elements through chemical reactions, characterized by high metal recovery rates and a high degree of resource reuse. Furthermore, hydrometallurgy has a wide range of applications and offers certain environmental advantages compared to pyrometallurgy. However, this method is relatively complex to operate, consumes more energy, and requires large quantities of chemical reagents, leading to increased costs. In addition, it places higher demands on the equipment used.

[0005] Biometallurgy, as an emerging green recycling technology, utilizes microorganisms or their metabolites to extract metal elements from spent batteries. It boasts advantages such as low cost, low pollution, and low energy consumption, and the microorganisms can be reused. However, biometallurgy is limited by the long cultivation and utilization time of the microorganisms, as well as the relatively long reaction time. Cultivating highly efficient microorganisms is challenging, and the extraction conditions are difficult to control precisely, which limits its potential for large-scale application.

[0006] Direct recycling technology is a novel battery recycling method that has emerged in recent years. Its core objective is to achieve efficient resource recovery while preserving the performance of the original materials to the greatest extent possible. This technology has the advantages of high resource recovery efficiency, relatively low cost, low energy consumption, and is more environmentally friendly; however, it also has disadvantages such as high technical requirements, difficulty in removing impurities, limited applicability, and difficulty in guaranteeing the structure, electrochemical performance, and stability of the recycled materials.

[0007] Therefore, there is an urgent need to provide a new hydrothermal reconstruction-precision lithium replenishment process to solve the core problems faced by existing cathode material regeneration technologies, such as lithium source waste, structural damage, unstable electrochemical performance, and complex processes. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention proposes a hydrothermal reconstruction-precision lithium replenishment process.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] One of the technical solutions of this invention:

[0011] A hydrothermal reconstruction-precision lithium replenishment process includes the following steps:

[0012] (1) The positive electrode sheet in the waste lithium-ion battery is sintered and sieved to obtain D-NCM111;

[0013] (2) Add water to the D-NCM111 to carry out a hydrothermal reaction, and then wash and dry it in sequence to obtain the hydrothermal product (H-NCM111);

[0014] (3) The hydrothermal product (H-NCM111) and the lithium source are added to a solvent and ground to obtain the lithium supplement product (H-NCM111-Li);

[0015] (4) Anneal the lithium supplement product (H-NCM111-Li) to obtain the recycled material (R-NCM111).

[0016] Optionally, the sintering conditions described in step (1) are: sintering at 550°C for 4 hours.

[0017] Beneficial effects: This invention disassembles and sinters the retired lithium-ion battery, which can remove organic binders and other impurities from the positive electrode, preparing it for subsequent hydrothermal reactions.

[0018] Optionally, the ratio of D-NCM111 to water in step (2) is 1000mg-2000mg:30ml; preferably 1000mg:30ml.

[0019] Optionally, the conditions for the hydrothermal reaction process described in step (2) are: reaction at 200°C for 3 hours.

[0020] Beneficial effects: Under the hydrothermal reaction conditions defined in this invention, without the need to add a lithium source, elements such as lithium, nickel, cobalt, and manganese in D-NCM111 will undergo redistribution and structural adjustment under high temperature and high pressure, removing impurity phases from the material surface and reducing particle agglomeration, thereby achieving preliminary restoration of the material structure. This step eliminates the need for additional lithium sources, avoiding lithium waste and the formation of grain boundary impurity phases caused by excessive lithium, and also avoids the waste liquid treatment of large amounts of lithium solution.

[0021] Optionally, the drying conditions in step (2) are: drying in a vacuum at 80-120°C for 10 hours.

[0022] Optionally, in step (3), the amounts of lithium, nickel, cobalt, and manganese in the hydrothermal product (H-NCM111) are determined by ICP, and the amount of lithium source added must meet the following requirements:

[0023] The ratio of n(Li) / [n(Ni)+n(Co)+n(Mn)] in H-NCM111-Li is 1.00-1.15, preferably 1.00, 1.05, 1.10, or 1.15; more preferably 1.10.

[0024] Furthermore, the solvent is anhydrous ethanol.

[0025] Beneficial effects: The purpose of the lithium replenishment step defined in this invention is to precisely adjust the lithium content in the material, thereby changing the original stoichiometry of the waste material. ICP measurement can accurately obtain the content of each element in the material, thus achieving precise lithium replenishment. The addition of anhydrous ethanol helps to improve the mixing uniformity of the material during the grinding process.

[0026] Furthermore, the lithium source is lithium hydroxide monohydrate (LiOH·H2O) or lithium carbonate.

[0027] Optionally, the conditions for the annealing process in step (4) are: heating to 800°C at a rate of 5°C / min in an air atmosphere, holding at that temperature for 5 hours, and then cooling to room temperature in the furnace.

[0028] Beneficial effects: The annealing process defined in this invention can not only replenish the lithium source into the crystal structure, but also further eliminate defects in the material, thereby improving the crystallinity and electrochemical performance of the material.

[0029] The second technical solution of this invention:

[0030] A recycled material for assembling button-type half-cells is prepared by the above-mentioned hydrothermal reconstruction-precision lithium replenishment process.

[0031] The third technical solution of this invention:

[0032] A button-type half-cell, wherein the above-mentioned recycled material is used as the active material in the positive electrode.

[0033] Compared with the prior art, the present invention has the following advantages and technical effects:

[0034] (1) Reduce lithium source consumption costs

[0035] By repairing the crystal structure of materials through hydrothermal reaction, the drawback of traditional methods that require the addition of excessive LiOH or Li2CO3 is avoided, thereby reducing the cost of lithium sources.

[0036] (2) Restoring the crystal structure and properties of materials

[0037] The NCM111 layered structure was gently reconstructed under hydrothermal conditions (200℃, 3 hours), and combined with precise lithium replenishment through annealing, enabling the initial discharge specific capacity of the recycled material to be restored to 138 mAh g. -1 The capacity retention rate is relatively high after about 100 cycles.

[0038] (3) Simplify the process and reduce pollution

[0039] It eliminates the multi-step precipitation and extraction processes of traditional hydrometallurgy, reduces the discharge of waste acid / alkali solutions, and avoids the high-temperature energy consumption (1200℃→800℃) of pyrometallurgy, thus reducing CO2 emissions.

[0040] (4) Achieve efficient industrial production

[0041] After determining the lithium content by ICP, lithium is precisely replenished to ensure uniform lithium distribution and avoid the formation of grain boundary impurities caused by excessive lithium, resulting in good consistency of recycled materials and meeting the needs of large-scale production. Attached Figure Description

[0042] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0043] Figure 1 In the middle, (a) and (b) are D-NCM111, (c) and (d) are H-NCM111, (e) and (f) are R-NCM111-1.10, and (g) and (h) are SEM images of C-NCM111 samples;

[0044] Figure 2 The ICP test bar charts of H-NCM111 prepared by adding 3 mol / L, 4 mol / L, 5 mol / L and 0 mol / L to the hydrothermal reaction of Comparative Example 1, respectively;

[0045] Figure 3 (a) shows the XRD patterns of C-NCM111, D-NCM111, R-NCM111-1.10, and H-NCM11110-80°; (b) shows the XRD patterns of 18-20°; and (c) shows the XRD patterns of 64-67°.

[0046] Figure 4 XPS spectra of Ni, Co and Mn in C-NCM111, D-NCM111, R-NCM111-1.10 and H-NCM111; where (a) is Ni, (b) is Co and (c) is Mn.

[0047] Figure 5Electrochemical cycle performance test graphs of coin cells made from C-NCM111, D-NCM111 and NCM111 regenerated with different lithium replenishment amounts in Example 1.

[0048] Figure 6 The graphs show the first three cyclic voltammetry tests of D-NCM111;

[0049] Figure 7 The graphs show the first three cyclic voltammetry tests of R-NCM111-1.10;

[0050] Figure 8 Electrochemical impedance spectroscopy for D-NCM111, R-NCM111-1.10, and C-NCM111;

[0051] Figure 9 The discharge specific capacity diagrams for D-NCM111 and R-NCM111-1.10 at different discharge rates are shown. Detailed Implementation

[0052] Current recycling processes for spent lithium batteries often involve lithium replenishment during the hydrothermal process. However, for ternary lithium batteries, this process significantly increases lithium consumption. Furthermore, due to the small interlayer spacing of NCM111 layered materials, lithium ions struggle to embed within the layered structure, creating a large reaction barrier and resulting in poor replenishment effectiveness, failing to adequately restore the electrochemical performance of ternary lithium-ion batteries. Therefore, this invention creatively alters the timing of lithium replenishment, disclosing a hydrothermal reconstruction-precision lithium replenishment process, comprising the following steps:

[0053] (1) The positive electrode sheet in the waste lithium-ion battery is sintered and sieved to obtain D-NCM111;

[0054] (2) Add water to the D-NCM111 to carry out a hydrothermal reaction, and then wash and dry it in sequence to obtain the hydrothermal product (H-NCM111);

[0055] (3) The hydrothermal product (H-NCM111) and the lithium source are added to a solvent and ground to obtain the lithium supplement product (H-NCM111-Li);

[0056] (4) Anneal the lithium supplement product (H-NCM111-Li) to obtain the recycled material (R-NCM111).

[0057] In an optional embodiment, the sintering conditions in step (1) are: sintering at 550°C for 4 hours, under which organic binders and other impurities in the positive electrode can be removed, in preparation for the subsequent hydrothermal reaction.

[0058] In an optional embodiment, the ratio of D-NCM111 to water in step (2) is 1000-2000 mg: 30 ml.

[0059] In an optional embodiment, the hydrothermal reaction process in step (2) is carried out under the following conditions: reaction at 200°C for 3 hours. Under these hydrothermal reaction conditions, no lithium source needs to be added. The lithium, nickel, cobalt, manganese, and other elements in D-NCM111 will undergo redistribution and structural adjustment under high temperature and high pressure, removing impurity phases from the material surface and reducing particle agglomeration, thereby achieving preliminary restoration of the material structure. This step does not require the addition of an extra lithium source, avoiding lithium source waste and the problem of grain boundary impurity phase formation caused by excessive lithium, and also avoiding the waste liquid treatment of a large amount of lithium solution.

[0060] In an optional embodiment, the drying conditions in step (2) are: drying under vacuum at 80-120°C for 10 hours.

[0061] In an optional embodiment, in step (3), the amounts of lithium, nickel, cobalt, and manganese in the hydrothermal product (H-NCM111) are determined by ICP, and the amount of lithium source added must meet the following requirements:

[0062] The ratio of n(Li) / [n(Ni)+n(Co)+n(Mn)] in H-NCM111-Li is 1.00-1.15, preferably 1.00, 1.05, 1.10, or 1.15; more preferably 1.10. The purpose of the defined lithium replenishment step is to precisely adjust the lithium content in the material, thereby changing the original stoichiometric ratio of the waste material. ICP determination (a conventional technique) can accurately obtain the content of each element in the material, thus achieving precise lithium replenishment.

[0063] In a preferred embodiment, the solvent is anhydrous ethanol. The addition of anhydrous ethanol helps to improve the mixing uniformity of the materials during the grinding process.

[0064] In a preferred embodiment, the lithium source is lithium hydroxide monohydrate (LiOH·H2O) or lithium carbonate.

[0065] In an optional embodiment, the annealing process in step (4) is as follows: the temperature is raised to 800°C at a rate of 5°C / min in an air atmosphere, held for 5 hours, and then cooled to room temperature in the furnace. This annealing process can supplement the lithium source into the crystal structure and further eliminate defects in the material, thereby improving the crystallinity and electrochemical performance of the material.

[0066] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0067] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0068] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0069] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0070] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0071] All raw materials used in this invention were purchased from the market.

[0072] The technical solution of the present invention will be further illustrated by the following embodiments.

[0073] Example 1

[0074] A hydrothermal reconstruction-precision lithium replenishment process includes the following steps:

[0075] 1. Preprocessing

[0076] Lithium-ion batteries (ternary) retired from electric vehicles were selected, and the positive electrode sheets were separated after disassembly. The positive electrode sheets were sintered at 550℃ for 4 hours, ground, and passed through a 300-mesh sieve to obtain D-NCM111 (n(Ni):n(Co):n(Mn):n(Li) = 1:0.991:0.976:2.671). The purpose of this step is to remove organic binders and other impurities from the positive electrode sheets, preparing them for the subsequent hydrothermal reaction.

[0077] 2. Hydrothermal reaction

[0078] 1000 mg of D-NCM111 was placed in a 50 ml hydrothermal reactor, and 30 ml of deionized water was added. No additional lithium source or other materials were added. The reactor was placed in a forced-air drying oven and reacted at 200°C for 3 hours. After the reactor cooled, the product was washed three times with water and placed in a vacuum drying oven at 90°C for 10 hours to obtain the hydrothermal product (H-NCM111).

[0079] 3. Lithium supplementation

[0080] The amount of lithium, nickel, cobalt, and manganese in the hydrothermal product (H-NCM111) was determined by ICP. Based on the determination results, lithium hydroxide monohydrate (LiOH·H2O) was added in a certain stoichiometric ratio to make the n(Li) / [n(Ni)+n(Co)+n(Mn)] values ​​of H-NCM111-Li reach 1.00, 1.05, 1.10, and 1.15, respectively. Lithium hydroxide monohydrate and H-NCM111 were poured into a mortar, a small amount of anhydrous ethanol was added, and manual grinding began until all the anhydrous ethanol evaporated. The lithium-added product (H-NCM111-Li) was collected. According to the method of this embodiment, the amount of lithium hydroxide monohydrate consumed per 1000 mg of regenerated material (D-NCM111 material) is less than 200 mg.

[0081] 4. Annealing

[0082] The lithium-added product (H-NCM111-Li) was placed in an alumina crucible and sintered in a muffle furnace, i.e., heated to 800°C at a rate of 5°C / min in air atmosphere, held at that temperature for 5 hours, and then cooled to room temperature with the furnace to obtain the regenerated product (R-NCM111).

[0083] Comparative Example 1

[0084] Using the traditional hydrothermal regeneration method for lithium replenishment, more than 5000 mg of lithium hydroxide monohydrate (or other lithium sources) is required for every 1000 mg of material (from the same batch as in Example 1). Furthermore, the traditional hydrothermal method has poor lithium replenishment efficiency because there is a significant reaction barrier for lithium ions to intercalate into the crystal lattice, making lithium replenishment difficult.

[0085] The traditional hydrothermal regeneration method for lithium replenishment involves the following steps:

[0086] First, the failed NCM111 material (D-NCM111) was subjected to hydrothermal treatment: 1000mg of waste NCM111 electrode material was accurately weighed, transferred to a 50mL high-pressure reactor, 30mL of 4mol / L LiOH solution was added, and after sealing, it was placed in a 220℃ forced-air drying oven for 4h to complete the hydrothermal treatment.

[0087] After the hydrothermal reaction is complete, allow the reactor to cool naturally to room temperature. Remove the product and wash it repeatedly by centrifugation with deionized water until the pH of the supernatant stabilizes at 7.0±0.2 (to ensure complete removal of residual alkali from the material surface). Transfer the washed product to a 100℃ vacuum drying oven for drying.

[0088] The dried product was mixed with a certain amount of Li₂CO₃ powder (calculated according to the stoichiometric ratio of the target product, with Li element in excess by 5%, i.e., the amount of lithium carbonate added satisfies n(Li) / [n(Ni)+n(Co)+n(Mn)] reaching 1.05), and thoroughly ground in an agate mortar for 30 min until uniformly mixed. The mixture was then transferred to a corundum crucible. The crucible was placed in a tube furnace and heated to 850℃ at a rate of 5℃ / min in an oxygen atmosphere. After holding at this temperature for 4 h, it was cooled to room temperature with the furnace to finally obtain the regenerated NCM111 cathode material.

[0089] In Comparative Example 1, lithium hydroxide monohydrate at concentrations of 3 mol / L, 4 mol / L, 5 mol / L, and 0 mol / L was added to the hydrothermal reaction, respectively. After the hydrothermal reaction, the mixture was washed three times with water and dried. The resulting four groups of H-NCM111 samples were analyzed for ICP, and the lithium replenishment effect was minimal. The results are as follows: Figure 2 As shown.

[0090] Figure 2 The image shows the ICP bar charts of H-NCM111 prepared by adding 3 mol / L, 4 mol / L, 5 mol / L and 0 mol / L lithium sources to the hydrothermal reaction of Comparative Example 1, respectively. As can be seen from the figure, the lithium replenishment effect is not significantly different whether a lithium source is added or not during the hydrothermal reaction. However, D-NCM111 has a higher lithium content because there may be some lithium salt impurities on the surface of the material. After the hydrothermal reaction, these impurities are removed, resulting in a lower lithium content.

[0091] Effect verification

[0092] Excellent recovery of material structure and properties

[0093] (1) Microscopic morphology analysis

[0094] C-NCM111 (commercial material, purchased from KELU);

[0095] D-NCM111 (waste materials);

[0096] H-NCM111 (Hydrothermal material);

[0097] R-NCM111 (recycled material);

[0098] Figure 1SEM images of samples D-NCM111, H-NCM111, R-NCM111-1.10, and C-NCM111 are shown. The surface morphology and microstructure of the D-NCM111, H-NCM111, R-NCM111, and C-NCM111 samples were characterized using scanning electron microscopy (SEM), and the results are as follows. Figure 1 As shown. By Figure 1 As can be seen from (a) and (b) (SEM images of D-NCM111), although the sample still maintains a spherical outline, obvious cracks have appeared inside the particles; at the same time, the phenomenon of primary particle detachment on the surface of the spherical particles was observed, indicating that the structure and morphology of D-NCM111 have been damaged. Figure 1 Figures (c) and (d) show the SEM characterization results of H-NCM111. As can be seen from the figures, after hydrothermal treatment, the dispersibility of D-NCM111 particles is significantly improved, and impurities on the particle surface are completely eliminated. This phenomenon indicates that hydrothermal reaction can effectively dissolve lithium salt impurities on the particle surface, ensuring the smooth progress of the subsequent regeneration process. Figure 1 Images (e) and (f) show the SEM morphology characteristics of R-NCM111-1.10. After annealing, the recycled material exhibits reduced agglomeration compared to D-NCM111, with a more regular overall particle morphology and good small particle dispersion. However, compared to the commercial material C-NCM111... Figure 1 Compared to (g) and (h), the aggregate morphology shows significant differences. This may be because the waste NCM111 was originally polycrystalline; after recycling, the dense polycrystalline particles gradually become loose and pulverize, leading to the separation of some primary particles. Additionally, some primary particles that were about to separate may have already separated during the regeneration process. The figure clearly shows a significant increase in the number of small particles in the recycled material.

[0099] Figure 3 XRD patterns of C-NCM111, D-NCM111, R-NCM111-1.10, and H-NCM111; from Figure 3 As can be seen in (a), all samples exhibit a typical hexagonal α-NaFeO2 layered structure, belonging to the space point group. During the charging and discharging process of a lithium-ion battery, lithium ions shuttle between the positive and negative electrodes. During charging, lithium ions are released from the positive electrode material, leaving vacancies. Because Ni... 2+ The ionic radius (0.069 nm) of Li + The ionic radii (0.076 nm) are close to those of Ni, and under the influence of electrostatic repulsion between oxygen layers, Ni... 2+The presence of lithium sites leads to Li / Ni mixing, causing capacity decay. Li / Ni mixing causes a change in the phase structure of the cathode material, transforming it from a layered structure to a spinel structure and a cubic rock salt phase structure, gradually diffusing from the surface into the bulk phase. By comparing the intensity ratio (I(003) / I(104)) of the (003) and (104) diffraction peaks, the degree of lithium-nickel mixing in different materials can be preliminarily assessed. Specifically, when I(003) / I(104) is greater than 1.20, the degree of cation mixing is low, and the electrochemical performance is good. The I(003) / I(104) value of D-NCM111 is 0.92, indicating severe lithium-nickel mixing and a large amount of rock salt phase structure; while the I(003) / I(104) value of R-NCM111 is greater than 1.20, confirming that the degree of lithium-nickel mixing in R-NCM111 is significantly reduced after regeneration, and the rock salt phase has recovered to a layered structure.

[0100] To gain a deeper understanding of the recovery trend of the layered structure, the changes in the (003) diffraction peak were investigated in detail. Figure 3 (b) shows the XRD pattern in the 18-20° range. The results show that the (003) diffraction peak of D-NCM111 shifts to a lower angle and the peak shape is significantly broadened. This is due to the repulsive effect between oxygen layers along the c-axis under lithium-deficient conditions, which leads to an increase in the cell parameter c value. After hydrothermal reaction, the (003) diffraction peak shifts slightly to a higher angle, but does not return to the position of C-NCM111. After lithium replenishment annealing, the (003) diffraction peak of R-NCM111-1.10 returns to the initial angle and completely matches the diffraction peak position of C-NCM111, indicating that its layered structure recovery effect is excellent. Previous studies have also proven that the (003) peak diffraction angle of the repaired cathode material is restored to a higher angle.

[0101] Figure 3 Image (c) shows the XRD patterns in the 64-67° range, illustrating the variations in the (108) and (110) diffraction peaks for different materials. Typically, the degree of splitting of the (108) / (110) diffraction peak pair is a key indicator for determining whether a material has a layered structure. The splitting of the (110) / (108) diffraction peaks is related to a decrease in lattice parameters, which is due to the Ni... 3+ Compared to Ni 2+ The smaller effective ionic radius leads to a decrease in the average metal-metal distance, which in turn reduces the lattice parameter. The (008) / (110) diffraction peaks after regeneration show obvious splitting, indicating that the crystal structure has been restored to an ordered hexagonal layered structure.

[0102] (2) Surface transition metal chemical valence state analysis

[0103] Figure 4XPS spectra of Ni, Co, and Mn elements in C-NCM111, D-NCM111, R-NCM111-1.10, and H-NCM111 are shown in the figure. XPS measurements were performed to reveal the changes in valence states of elements, including Ni, Co, and Mn, in NCM111 in order to further understand the role of hydrothermal regeneration of waste ternary materials.

[0104] like Figure 4 As shown in (a), the XPS spectrum of the Ni 2p orbital exhibits two main binding energy peaks and two satellite peaks. Peak fitting analysis reveals that the spectral peaks of the Ni 2p orbital can be decomposed into Ni 2p orbital peaks. 3+ and Ni 2+ Two chemical states, of which Ni 3+ Corresponding 2p 3 / 2 and 2p 1 / 2 The orbital binding energies are located at 855.4 eV and 873.3 eV, respectively, while Ni 2+ Corresponding 2p 3 / 2 and 2p 1 / 2 The orbital binding energies are 854.6 eV and 871.8 eV, respectively. Quantitative analysis results show that Ni in D-NCM111, H-NCM111, R-NCM111-1.10, and C-NCM111... 3+ The relative contents were 51.35%, 55.09%, 58.66%, and 59.81%, respectively. Correspondingly, Ni... 2+ The proportions were 48.65%, 44.91%, 41.34%, and 40.19%, respectively. It is worth noting that Ni in D-NCM111... 2+ / Ni 3+ The ratio is significantly higher than that of R-NCM111, indicating the presence of a NiO rock salt phase on the surface of D-NCM111. This also suggests a more severe lithium-nickel mixing phenomenon in D-NCM111. Furthermore, the rock salt phase in H-NCM111 has not been completely eliminated, possibly because while the high-temperature, high-pressure environment of the hydrothermal reaction can degrade some impurity phases in D-NCM111, it is difficult to achieve complete structural recovery. In stark contrast, the NiO ratio in R-NCM111 is significantly higher than that in R-NCM111. 3+ / Ni 2+ The ratio is basically consistent with that of C-NCM111, indicating that the degree of cation mixing in the recycled ternary material has been significantly improved, which is of positive significance for improving the electrochemical performance of the material.

[0105] Normally, Mn and Co do not participate in redox processes during electrochemical reactions. XPS test results further confirm this characteristic of Co, namely, Co is present as Co in all tested materials. 3+The form of Mn exists stably, and no characteristic peaks of other valence states were observed. However, Mn was detected in both D-NCM111 and H-NCM111 samples. 3+ The characteristic peaks, with relative proportions of 24.8% and 17.17%, respectively, may be the result of the synergistic effect of material structure degradation and electrolyte side reactions during battery cycling. Specifically, the repeated expansion and contraction of the lattice during cycling leads to a decrease in the stability of the layered structure, while corrosive species such as HF generated by electrolyte decomposition may trigger Mn... 4+ The reduction and dissolution of Mn ultimately led to the formation of Mn 3+ The generation of Mn. 3+ The presence of Mn significantly exacerbates the performance degradation of materials: on the one hand, Mn 3+ The Jahn-Teller effect induces lattice distortion, hindering the Li + The diffusion kinetics; on the other hand, compared to Mn 4+ Mn 3+ It exhibits a stronger tendency to dissolve, accelerating the loss of transition metal ions, ultimately leading to continuous capacity decay and shortened cycle life. Notably, after high-temperature annealing, the Mn content in the R-NCM111 sample... 3+ The complete disappearance of the characteristic peaks indicates that the Mn element has returned to the +4 stable state, and the chemical valence characteristics of the material have returned to the level of commercial NCM111, which provides an important basis for the performance restoration of the material.

[0106] (3) Electrochemical performance analysis

[0107] Electrode preparation and battery assembly

[0108] The electrode to be tested was prepared using a standard laboratory ratio: active material, polyvinylidene fluoride (PVDF) and acetylene black were weighed in a mass ratio of 8:1:1, thoroughly mixed, and then uniformly coated onto the surface of aluminum foil. After vacuum drying, the mixture was cut into circular electrode sheets.

[0109] The button cell assembly was completed in an argon-filled glove box, where humidity and oxygen content were strictly controlled below 0.1 ppm. A CR-2032 type button half-cell structure was used, with a lithium metal sheet as the counter electrode (negative electrode) and the aforementioned prepared circular electrode as the working electrode.

[0110] The assembled button cells were then subjected to performance tests such as cycle life, rate capability, CV, and impedance using the Newway testing system.

[0111] I. Long-cycle performance analysis of charge and discharge

[0112] The assembled button batteries underwent electrochemical performance testing using the Xinwei testing system. The test protocol was as follows: first, two activation cycles were performed at a 0.2C rate, followed by 100 consecutive cycles at a 1C rate to examine the charge-discharge performance and cycle stability of the materials. The test subjects included waste NCM111 (D-NCM111), commercial NCM111 (C-NCM111), and four types of regenerated NCM111 with different lithium replenishment amounts (labeled as R-NCM111-1.00, R-NCM111-1.05, R-NCM111-1.10, and R-NCM111-1.15, respectively).

[0113] Figure 5 Electrochemical cycle performance test graphs for coin cells fabricated from C-NCM111, D-NCM111, and NCM111 regenerated in Example 1 with different lithium replenishment amounts are provided by [source missing]. Figure 5 As can be seen, the electrochemical performance of NCM111 material was significantly improved after regeneration. Specific data are as follows:

[0114] In the first discharge test at 1C rate, the discharge specific capacity of D-NCM111 was only 71.86 mAh g. -1 Meanwhile, the discharge specific capacity of recycled materials all showed a significant improvement, with R-NCM111-1.00, R-NCM111-1.05, R-NCM111-1.10, and R-NCM111-1.15 having discharge specific capacities of 98.33, 124.73, 138.03, and 131.77 mAh g, respectively. -1 The first-cycle discharge specific capacity of the commercially available material C-NCM111 is 135.92 mAh g. -1 The initial discharge specific capacity of R-NCM111-1.10 is nearly double that of D-NCM111 and is basically on par with the commercial material C-NCM111.

[0115] After 100 cycles, the discharge specific capacities of D-NCM111, R-NCM111-1.00, R-NCM111-1.05, R-NCM111-1.10, R-NCM111-1.15, and C-NCM111 were 62.39, 63.42, 82.85, 131.75, 114.81, and 130.72 mAh g, respectively. -1 Among them, R-NCM111-1.10 has a capacity retention rate of up to 95.45%, which is basically consistent with C-NCM111's 96.17%, demonstrating excellent cycle stability.

[0116] In summary, the test results show that the D-NCM111 material has poor electrochemical performance, while the four NCM111 materials prepared by this regeneration method with different lithium replenishment amounts all exhibited significantly improved discharge specific capacity and cycle stability. In particular, the regenerated material with a lithium replenishment amount of 1.10 (R-NCM111-1.10) showed electrochemical performance approaching that of commercially available NCM111, confirming the significant effectiveness of this regeneration method in repairing and improving the performance of NCM111 cathode materials.

[0117] II. Cyclic Voltammetry (CV) Analysis

[0118] Figure 6 The image shows the cyclic voltammetry (CV) curves for the first three cycles of D-NCM111, representing spent NCM111 material. The CV curves exhibit unique electrochemical behavior characteristics. During the three cycles, the redox peak in the first cycle shows a significant shift compared to subsequent cycles. This indicates that the spent material undergoes numerous irreversible reactions during the initial charge-discharge phase, such as side reactions on the electrode surface and minor structural damage due to prior use, thus interfering with normal lithium-ion migration. Furthermore, the large peak potential difference in the first cycle (ΔE = 0.345V) directly reflects severe electrode polarization in the spent material, significantly hindering the lithium-ion insertion / extraction process within the electrode. This indirectly demonstrates that after use, the structural integrity of the spent material is compromised, active sites are reduced or contaminated, greatly affecting the kinetics of lithium-ion insertion and extraction, leading to a decline in its electrochemical performance. The oxidation and reduction peaks correspond to the lithium ion extraction and insertion processes, respectively. The broad peak shape and large peak potential difference of D-NCM111 fully demonstrate that the waste material faces high resistance and poor reversibility in the lithium ion extraction and insertion reaction. The structural disorder problems such as internal lattice distortion and impurity accumulation restrict the performance of its electrochemical properties.

[0119] Figure 7The images show the cyclic voltammetry (CV) curves of R-NCM111-1.10 for the first three cycles. As a regenerated NCM111 material, R-NCM111-1.10 exhibits excellent electrochemical performance recovery. The CV curves for the first three cycles show high peak overlap and a small peak potential difference (ΔE = 0.105V) in the first cycle, strongly demonstrating a significant reduction in electrode polarization after regeneration and a substantial improvement in the reversibility of lithium-ion insertion / extraction. This indicates that the regeneration process successfully repaired the structural defects of the waste material. By reorganizing the crystal lattice, removing impurities, and supplementing active sites, lithium ions can migrate more smoothly during charge-discharge cycles, resulting in a significant improvement in electrode kinetics. The sharp and symmetrical oxidation and reduction peaks reflect that the regenerated material possesses a more ordered crystal structure and superior electrochemical activity, with low resistance and fast speed in lithium-ion insertion / extraction reactions, and stable electrochemical performance during charge-discharge processes. Compared with D-NCM111, it is clear that the regeneration process can effectively restore the electrochemical activity of NCM111 material and enhance its application potential as a cathode material for lithium-ion batteries. This indicates that the regenerated material has better reversibility and kinetic characteristics in the redox reaction of lithium-ion insertion and extraction.

[0120] III. Electrochemical Impedance Spectroscopy (EIS)

[0121] Figure 8 The figure shows the electrochemical impedance spectroscopy (EIS) spectra of three NCM111 materials (D-NCM111, R-NCM111-1.10, and C-NCM111), and the fitting results of their impedance data are shown in Table 1.

[0122] Table 1. Fitting results of impedance spectrum data

[0123] Material Rs Rct Wo D-NCM111 3.94 71.03 72.60 R-NCM111-1.10 3.49 31.14 12.13 C-NCM111 3.48 30.85 11.75

[0124] Depend on Figure 8 As shown in Table 1, the ohmic impedance (Rs) values ​​of the three materials are relatively similar. This indicates that the systematic error has a basically consistent impact on the three materials during the selection and assembly of the coin cell, and impedance deviations caused by experimental operation or material substrate differences can be ruled out.

[0125] Analysis of the interfacial transfer impedance (Rct) showed that the Rct of D-NCM111 was 71.03 Ω, significantly higher than the other two materials. This is likely due to the formation of a thick passivation layer on the surface of the waste material (D-NCM111). This passivation layer originates from the deterioration of the material's surface structure (such as changes in elemental valence states and impurity deposition), thus hindering the charge transfer process at the electrode / electrolyte interface. After regeneration, the Rct of R-NCM111-1.10 decreased to 31.14 Ω, close to the 30.85 Ω of the commercial material C-NCM111, indicating that the regeneration process effectively repaired the defective structure of the material surface, restoring the interfacial charge transfer capability to a level essentially equivalent to that of commercial materials.

[0126] The variation of diffusion migration resistance (Wo) follows the same pattern as Rct: D-NCM111 exhibits a Wo as high as 72.60 Ω, indicating that the diffusion process of lithium ions in its bulk phase or interface is severely hindered; while R-NCM111-1.10 shows a Wo that decreases to 12.13 Ω, close to the 11.75 Ω of C-NCM111. A higher Wo value indicates worse lithium-ion diffusion kinetics. This result further confirms that regeneration treatment significantly improves the diffusion channels of lithium ions in the material (e.g., eliminating lattice distortion and reducing lithium vacancy defects), resulting in a substantial improvement in diffusion performance that approaches the level of commercially available materials.

[0127] IV. Ratio Performance Analysis

[0128] Figure 9 The discharge specific capacity graphs for D-NCM111 and R-NCM111-1.10 at different rates are shown. Rate performance testing is one of the key tests for evaluating the electrochemical performance of ternary materials. The discharge specific capacities of D-NCM111 and R-NCM111-1.10 at different rates were compared and analyzed. The test rate range was set from 0.2 to 5C, then back to 0.2C. Five cycles of testing were performed at each rate. The results are shown below. Figure 9 As shown. At test rates of 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C, the discharge capacity of R-NCM111-1.10 was 149.92 mAh g⁻¹. -1 122.21mAh g -1 138.74mAh g -1 131.53mAhg -1 and 118.81mAh g -1 When the discharge rate returns to 0.2C, the discharge specific capacity recovers to 148.46 mAh g. -1 This demonstrates better capacity recovery and rate performance. In contrast, the rate performance of the recycled ternary materials is poor, with a discharge capacity of only 85.95 mAh g⁻¹ at the same rate. -173.98mAh g -1 64.27mAh g -1 52.11mAh g -1 and 34.36mAh g -1 When the discharge rate returns to 0.2C, the specific capacity is 85.04 mAh g. -1 In summary, the recycling process effectively optimizes the electrochemical performance of ternary materials. R-NCM111-1.10 exhibits superior characteristics in terms of rate adaptability, capacity recovery, and cycle stability, providing strong data support for the recycling of waste ternary materials.

[0129] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A hydrothermal reconstruction-precision lithium replenishment process, characterized in that, Includes the following steps: (1) The positive electrode sheet in the waste battery is sintered and sieved to obtain D-NCM111; (2) Add water to the D-NCM111 to carry out a hydrothermal reaction, and then wash and dry it in sequence to obtain H-NCM111; (3) Add the H-NCM111 and lithium source to a solvent and grind them to obtain H-NCM111-Li; (4) Anneal the H-NCM111-Li to obtain the recycled material R-NCM111.

2. The hydrothermal reconstruction-precision lithium replenishment process according to claim 1, characterized in that, The sintering conditions described in step (1) are: sintering at 550°C for 4 hours.

3. The hydrothermal reconstruction-precision lithium replenishment process according to claim 1, characterized in that, The ratio of D-NCM111 to water in step (2) is 1000-2000mg:30ml.

4. The hydrothermal reconstruction-precision lithium replenishment process according to claim 1, characterized in that, The conditions for the hydrothermal reaction process described in step (2) are: reaction at 200℃ for 3 hours.

5. The hydrothermal reconstruction-precision lithium replenishment process according to claim 1, characterized in that, The drying conditions described in step (2) are: drying for 10 hours under vacuum at 80-120°C.

6. The hydrothermal reconstruction-precision lithium replenishment process according to claim 1, characterized in that, The amount of lithium source added in step (3) must meet the following requirements: The ratio of n(Li) / [n(Ni)+n(Co)+n(Mn)] in H-NCM111-Li is 1.00-1.

15.

7. The hydrothermal reconstruction-precision lithium replenishment process according to claim 6, characterized in that, The lithium source is lithium hydroxide monohydrate or lithium carbonate.

8. The hydrothermal reconstruction-precision lithium replenishment process according to claim 1, characterized in that, The conditions for the annealing process described in step (4) are: heating to 800°C at a rate of 5°C / min in an air atmosphere, holding at that temperature for 5 hours, and then cooling to room temperature in the furnace.

9. A recycled material for assembling button-type half-cells, characterized in that, It is prepared by the hydrothermal reconstruction-precision lithium replenishment process according to any one of claims 1-8.

10. A button-type half-cell, characterized in that, The recycled material described in claim 9 is used as the active material of the positive electrode.

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